On Sept. 28, 2000, the first CIA Predator drone took off from a base in Uzbekistan on its maiden flight and soon spotted “a tall man in flowing white robes” in a compound just outside Jalalabad, Afghanistan.

“While the resolution was not sufficient to make out the man’s face, I don’t know of any analyst who didn’t subsequently conclude that we were looking at (Osama bin Laden),” wrote former CIA director George Tenet in his memoir, "At the Center of the Storm."

The new drone was unarmed, however, having been developed not as a weapon, but as a long-range reconnaissance vehicle.

Wrote Tenet, “As technologically dazzling as that was, it was frustrating in almost equal measure. Yes, we might have been looking at (bin Laden), but we were not in a position to do anything about it.”

That frustration, say U.S. officials and analysts, drove the development of an armed Predator a year later. But the process was fraught with technical, legal and budgetary issues and the armed drone was not operational until after bin Laden’s henchmen had slammed passenger planes into the World Trade Center and the Pentagon on Sept. 11, 2001.

According to one U.S. intelligence analyst, who spoke with NBC News on condition of anonymity, the first consequence of the drone sighting of bin Laden was a series of “what if?” discussions.

"There was some debate about what we would have done if the Predator had been armed," the analyst said of the conversations at CIA headquarters. "Part of it was who would pay for the arming, whether it would be the Air Force or the CIA, but there was a legitimate question on who should be firing weapons at targets on behalf of the United States."

Lt. Gen. John “Soup” Campbell, the associate CIA director for military support at the time, agreed that the thorniest question was “literally who will pull the trigger.”

Still, the prospect of taking out the leader of al Qaeda proved alluring. The National Security Council authorized the CIA to begin deploying armed Predators, along with more of the unarmed remotely controlled aircraft, aiming to have them in the air by Sept. 1, 2011.

It was left to the CIA and Air Force to work out the details on cost-sharing and the legal and moral issues of having the military or an intelligence agency carry out the attacks against targets who were not legally enemy combatants.

There were also technical issues, particularly with arming the warhead.

"The initial tests in Nevada didn't go well," said the analyst, recalling that in one, the Hellfire warhead didn't arm properly and the missile tore through a building in the desert without detonating. "There had to be a number of adjustments through that year-long period."

Campbell said the Hellfire was an off-the-shelf solution, and not well-suited to its mission. “The Hellfire is an anti-armor, anti-tank weapon,” he said. “Ultimately, we came up with a better warhead.”

By July 2001, in Tenet's words, the CIA had its "hair on fire." New reports indicated an increase in intelligence reporting about al Qaeda readying a massive attack somewhere in the West.

On July 10, Tenet called Condoleezza Rice, then national security adviser to President George W. Bush, to lay out seven pieces of intelligence that indicated the increasing likelihood of an attack.

The warning came amid a still vigorous debate among U.S. officials: Should the U.S. deploy the Predator again in an unarmed mode or wait until the armed Predator was ready?

"There was pressure on the CIA to fly it in reconnaissance mode," said the analyst. "The counter argument was we didn't want to fly it and alert the bad guys."

A National Security Council "principals meeting" on Sept. 4, 2001, “was dominated by the same subject that had been lingering all summer long: whether the president should approve our request to fly the Predator in a weaponized mode,” Tenet wrote. “Unfortunately, the Predator still wasn’t ready to do that.”

The CIA director also remained skeptical that intelligence agencies should be pulling the trigger of a military weapon. Despite the presence of Tenet, Rice and Secretary of Defense Donald Rumsfeld, the issue remained unresolved.

A week later, approximately 3,000 people died in Pennsylvania, New York and Virginia in the al Qaeda-orchestrated hijackings of commercial airliners.

The intelligence analyst said the attack changed everything: “No more debate on cost-sharing or legalities. The warhead would have to work.”

On Sept. 17, Bush signed the NSC finding authorizing the use of the armed drone, and within weeks, unarmed Predators were flying over Afghanistan. Soon afterward, the first armed Predator was fitted with a Hellfire missile.

Things happened so quickly that the drone operators were first installed in a trailer at the edge of the parking lot at CIA headquarters.

On Oct. 7, the war against the Taliban and al Qaeda began and armed drones were in the sky. There were problems immediately, however, presaging issues that have affected the Predator to the present.

That night, said Campbell, who was at CIA headquarters, a Predator located and tracked a convoy in Afghanistan that U.S. intelligence believed carried an important passenger -- Taliban leader Mullah Muhammad Omar. After the convoy stopped at or near a mosque, a Hellfire was readied.

But a military lawyer at Central Command headquarters, in Tampa, Fla., refused to authorize a strike. For nearly three hours, said Campbell, the issue was debated. By the time an attack was approved, the target was out of reach.

Rumsfeld and Tenet were not pleased. "We cut off (Centcom's) feed for a while," the analyst said of their reaction. At the same time, better operating procedures were instituted.

A few weeks later, on Oct. 25, the Predator was used in an unplanned mission. Abdul ul-Haq, a Pashtun leader and CIA ally, entered Afghanistan on a mule from Pakistan to help lead the resistance, but was soon surrounded by Taliban fighters. He put in a call to associates in the U.S., who then called the CIA, said the analyst.

"Unfortunately, there were no American assets anywhere in the vicinity … (but the) CIA did have an armed Predator UAV close by," Tenet wrote. "We sent it looking for Haq. When we found him surrounded, Agency officers remotely fired the Predator’s single Hellfire missile, hoping to divert Haq’s attackers, but one missile was insufficient to the task. Haq was captured and executed on October 25."

The attack proved two things: The drone could quickly reach remote locations, but its use in tactical operations was limited.

"It was a last-minute call,” Campbell said of the mission. “… There was no planning, no coordination, no situational awareness.”

But the operation proved the Predator could find targets and successfully fire its missiles.

Three weeks later, on Nov. 16, those capabilities were put to use after a high-ranking bin Laden lieutenant, Mohammed Atef, the military commander of al Qaeda and its No. 3 leader, was found in a "safe house" in Kabul.

"An armed Predator located him and directed an F-16 strike," said the analyst. Once the F-16 did its work, the Predator took care of what the analyst called "squirters," militants who escaped the attack.

In the weeks that followed, said Campbell, the Predator was used in a variety of operations, including tactical strikes. Soon it became the weapon of choice for targeting suspected terrorists hiding in remote locations, far from U.S. military forces.

“The drone program has proven to be the single most effective tool in destroying al Qaeda’s leadership and infrastructure inside Pakistan. Nothing else we have done comes remotely close, “ said Roger Cressey, who was deputy for counter terrorism on the NSC staff in the Clinton and Bush administrations and now an NBC News terrorism analyst. “Every reason not to use the armed predator over Afghanistan evaporated when the first tower collapsed.”